DE 15 98 413 discloses an apparatus wherein a single sample is held in a sample holder. During the irradiation and detection of diffracted radiation, the drive means associated with the single sample holder cause the sample to perform a translation in combination with a rotation of the sample about an axis at right angles to the irradiated plane of the sample. The purpose of the sample movement during the irradiation and detection is to improve the so called “particle statistics” and to obtain more reliable reflection intensities, or intensities with reduced standard deviation.
A problem that is encountered when using the apparatus of DE 15 98 413 is that it is time consuming when a plurality of powder samples have to be analysed. This problem is particularly pertinent in case of high throughput experimentation. According to the known method each powder sample is prepared one by one in an associated single sample holder and placed in the apparatus for performing the powder diffraction analysis. Then the apparatus is set and aligned, whereupon irradiation and detection take places. Subsequently, the powder is removed and a further powder sample is prepared and so on. This results in an ineffective way of working and thus in a considerable loss of time.
In U.S. Pat. No. 6,111,930 a powder diffraction analysis apparatus is disclosed having a sample changer. Said changer has a plurality of ring-shaped containers each for receiving a sample. The containers are mounted on a linear magazine, such that the samples can be successively brought into the irradiation beam. This known apparatus allows for the spinning of ring-shaped container holding the irradiated sample about an axis perpendicular of the sample surface, which is a common approach to improve the particle statistics.
A problem that is encountered with other known powder diffraction analysis equipment using a 2D detector is that during detection of the diffraction radiation, single diffraction spots and arcs are often observed instead of rings, especially when organic crystalline material (such as pharmaceuticals) is irradiated. This may be the result of the fact that not all lattice planes of the crystalline powder material have been in reflection or not for the same time or same amount, because the crystals were not random oriented or only a few crystals were present. As a result, the peak intensities of the powder diffraction patterns are not correct, and no representative 1D-powder diffraction pattern (intensity vs. diffraction angle 2θ) is created after integration of the detected 2D diffraction patterns causing problems during comparison of diffraction patterns for identification.